Device for heating and/or frothing a beverage

ABSTRACT

A device for heating and/or frothing a beverage includes a first duct connectable to an upstream steam source and to downstream mixing means arranged to introduce and mix at least steam into said beverage, said first duct having a first valve configured to be opened and closed and to enable or prevent steam flow into the duct, and a second duct connectable to the upstream steam source and to said downstream mixing means, said second duct having a second valve configured to be opened and closed and to enable or prevent steam flow into the duct, wherein a first one of said two ducts comprises a Venturi assembly configured to operate by Venturi effect in order to mix air with said steam in said first one of said two ducts when a second one of said two ducts is closed.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 12/523,955 filed in the U.S. Patent and Trademark Office onJul. 21, 2009, which is a National Stage application under 35 U.S.C.§371 of International Application No. PCT/IB2008/50004, filed on Jan. 3,2008, which claims priority from European Patent Application No. EP07425030.9 filed on Jan. 23, 2007, the disclosures of which areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention generally relates to a device for heating and/orfrothing a beverage, e.g. milk, by means of steam.

More particularly, the present invention relates to a device applied toan espresso coffee machine for preparing hot milk or cappuccinos, and inthe following description reference is made to such application, whichis considered the preferred one.

BACKGROUND ART

The devices for heating and/or frothing milk are well known. Forinstance, a device for preparing frothed beverages to be used inconjunction with a machine for preparing coffee and other hot beveragesis known from document EP 0607759 A1.

The prior art device comprises a nozzle, which is controlled by a manualvalve and which has a first chamber for steam inlet and a second chamberfor steam outlet. The two chambers are connected through a passage, ofreduced cross-sectional size, where a hole communicating with thesurrounding environment is provided.

Steam flow through the passage with reduced cross-sectional size causes,by Venturi effect, a sufficient pressure decrease to ensure intake fromthe surrounding environment of air which, mixed with steam, exitsthrough the second chamber and is introduced into the liquid, e.g. milk,frothing it.

A first problem of such a prior art is that the nozzle is effective forpreparing frothed beverages, but it is ineffective for preparingnon-frothed hot beverages, since the passage with reducedcross-sectional size generally entails either introduction of both airand steam into the beverage, thereby frothing it, or the need for anaccurate control of the manual valve to limit steam inlet and theconsequent air admission by Venturi effect.

Of course, vapour inlet control entails the further problem that thetime necessary for preparing heated beverages is considerably higherthan that required for preparing frothed beverages.

An automated machine for preparing espresso coffee, comprising a devicefor producing hot or frothed milk to be added to the espresso coffee, isknown from document EP 0472272 A2.

The device of the prior art machine comprises two valves for steamintroduction through a duct located upstream of a chamber with narrowercross-sectional size than the duct: The chamber, operating by Venturieffect, comprises an orifice for air intake from the surroundingenvironment. The two valves in the device have different flow rates.

Consequently, opening the valve with higher flow rate results in agreater steam flow into the chamber and hence enables preparing frothedmilk, since pressure reduction in the chamber by Venturi effect is high.

Closing the valve with higher flow rate and opening the valve with lowerflow rate on the contrary enables preparing hot milk, since pressurereduction in the chamber by Venturi effect is minimum and henceinsufficient to enable air flow from the surrounding environment intothe chamber.

Such a prior art, while enabling preparing both hot and frothed milk,has in any case the problem that preparing hot milk generally requires avery long time, in any case longer than that required for preparingfrothed milk.

As the skilled in the art readily realises, such problem is veryannoying in public places, where the beverage preparation time must beextremely short to provide for both short service time and good clients'satisfaction.

Essentially, the Applicant has realised that devices ensuring extremelyreduced preparation time, especially in respect of hot beverages,irrespective of whether hot or frothed beverages are to be prepared, arenot commercially available.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a device for heatingand/or frothing a beverage, which device does not suffer from thedrawbacks of the prior art.

The object is achieved by the device for heating and/or frothing abeverage as claimed.

The present invention also relates to a method for heating and/orfrothing beverages, as well as to a machine for beverage preparationincluding the device.

The claims are integral part of the technical teaching provided here inrespect of the invention.

According to a preferred embodiment, the device according to theinvention comprises a first duct having a first opening and closingvalve for making steam flow into the duct, and a second duct having botha second opening and closing valve for making steam flow into the duct,and a Venturi assembly configured to operate by Venturi effect when thefirst valve is closed.

According to a further feature of the present invention, the Venturiassembly is connected to a third valve configured to prevent operationof the Venturi assembly by Venturi effect in certain situations.

According to another feature of the present invention, the valve openingand closing is controlled by a control unit controlled by a commandunit.

According to yet another feature of the present invention, the deviceincludes a temperature detector device for detecting the instanttemperature of the beverage, and the control unit is configured toselectively control, depending on the instant beverage temperatures, thevalve opening and closing in order to prepare heated and/or frothedbeverages.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features and advantages of the present inventionwill become apparent from the following description of preferredembodiments, made for exemplifying and non-limiting purposes inconnection with the accompanying drawings, in which elements denoted bya same or similar numerical reference correspond to components havingthe same or similar function and construction, and in which:

FIG. 1 is an overall diagram of the device according to the invention,in a preferred embodiment;

FIG. 2 shows a detail of the device of FIG. 1 in a further embodiment;and

FIG. 3 shows a detail of the device of FIG. 1 in a third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, a device 10 for heating and/or frothing a beverage19, e. g. milk, applied to an espresso coffee machine, includes firstand second ducts 21 and 22, respectively. The ducts have a common inletconnected to a boiler 12, of known type, arranged to generate, forinstance, pressurised steam, and a common outlet connected to a mixingelement 14, for instance a nozzle, of known type, arranged to introduceand mix pressurised steam, possibly including air, as it will bedescribed in detail below, into the liquid 19 contained for instance ina container.

The device 10 also includes a control unit 25 and a command unit 39,connected to control unit 25 and arranged, for instance, to transmitcommands from a user to control the operation of device 10.

As it will be described in detail below, control unit 25 is configuredto control the operation of device 10 by means of programs developedduring the device design phase and stored for instance in the samecontrol unit 25.

The first duct 21 comprises a first valve 31, for instance anelectrically-actuated valve with internal diameter 3.5 mm, the openingand closure of which can be controlled by control unit 25 in order toenable or prevent pressurised steam flow from boiler 12 to nozzle 14.

The second duct 22, preferably having internal diameter equivalent orsubstantially equivalent with that of the first duct, comprises, in anupstream section, a second valve 32, for instance anelectrically-actuated valve with internal diameter 3.5 mm, the openingand closure of which can be controlled by control unit 25 in order toenable or prevent pressurised steam flow from boiler 12 to nozzle 14. Ina downstream section, towards nozzle 14, the duct comprises a ductelement 22 a preferably operating by Venturi effect.

The duct element 22 a (Venturi assembly or Venturi) comprises a ductlength 42, for instance with diameter 2.5 mm, upstream and downstreamconnected to the second duct 22, and an orifice 43, for instance withdiameter 1.5 mm, formed in duct length 42 and directly communicatingwith the surrounding environment at atmospheric pressure, as shown inFIG. 2.

According to a preferred embodiment, shown in FIG. 1, the orifice isconnected to a valve 33 (Venturi valve), for instance anelectrically-actuated valve with diameter equal to the orifice diameter,the opening and closure of which can be controlled by control unit 25 inorder to enable or not to enable air inlet from the surroundingenvironment into Venturi 22 a or, conversely, to enable or not to enablesteam outlet from orifice 43 towards the surrounding environment.

According to a variant of the preferred embodiment, Venturi valve 33 isfor instance a nonreturn valve arranged to prevent the only steam outletfrom orifice 43 towards the surrounding environment. Of course, as theskilled in the art can readily realise, such a valve needs not to becontrolled by control unit 25.

According to a third embodiment, orifice 43 is connected to a furtherduct length 44 (FIGS. 1, 3) with smaller diameter than orifice 43, e.g.diameter 0.5 mm.

Such an embodiment, as it will be described in detail below, is capableof reducing the air amount admitted through Venturi 22 a and enablesattaining a finer frothing than attainable with orifice 43.

In all embodiments, a temperature detecting device 27, e.g. atemperature sensor or thermometer, is preferably provided, which isconnected, in known manner, to control unit 25 and is arranged totransmit to control unit 25 signals representing the temperature ofliquid 19 in which nozzle 14 is immersed for preparing heated and/orfrothed beverages.

Control unit 25 of device 10 is configured, as it will be described indetail below, to control the operation of device 10 through programsdeveloped during the device design phase and stored for instance in thesame control unit 25. It preferably comprises a microcontroller 51 ofknown type, e.g. a microcontroller model MB90F4097G by company Fujitsu,connected to or including a multiple-port input-output interface (I/Ointerface) 55.

In the preferred embodiment, I/O interface 55 is connected to the firstand second valves 31 and 32, respectively, to the temperature detectingdevice (thermometer) 27, to the command unit 39 and the Venturi valve33, if provided.

Command unit 39, e.g. a two-key keyboard, is arranged to transmit tocontrol unit 25, e.g. upon actuation of one of the keys, commands forstarting and/or stopping the various functions of device 10. Moreparticularly, in the preferred embodiment, command unit (keyboard) 39comprises a first key 39 a intended to command the control unit 25 toprepare a heated and frothed beverage, and a second key 39 bcorrespondingly intended to command to prepare a heated beverage. Mostpreferably, keyboard 39 is associated with or includes a signalling unit38, e.g. a buzzer or a LED, connected to control unit 25 and arranged toaudibly and/or visually signal the completion of the command sentthrough keys 39 a or 39 b, as described in detail below.

Device 10 is preferably associated also with a parameter setting unit37, for instance a keyboard with display, of known type, connected tocontrol unit 25 and arranged to set operation parameters of device 10,to be stored for instance in the control unit.

The operation of the device described above is disclosed hereinafterwith reference to the embodiment shown in FIG. 1, including Venturivalve 33 controlled by control unit 25.

Moreover, in describing the operation, a starting condition is assumedwhere the first and second valves 31 and 32 and Venturi valve 33 areclosed and nozzle 14 is immersed in the beverage or liquid (milk) 19contained in a container.

Lastly, it is also assumed that boiler 12 operates, for instance, in apressure range from 0.8 to 1.4 bars, and that a maximum milk heatingtemperature is envisaged, e.g. a temperature of 70° C. Of course, inother embodiments, the values of the above quantities may be differentfrom those indicated, without departing from the scope of what isdescribed and claimed.

The operation of device 10 for preparing a heated and frothed beverage,e.g. milk, is as follows.

Upon actuation, in a first phase, of key 39 a intended to startpreparation of heated and frothed milk, control unit 25, according tothe programs developed during the design phase of device 10, keepsVenturi valve 33 closed and commands the opening of both the first valve31 and the second valve 32, which therefore enable a quick steam flowfrom nozzle 14 and a correspondingly quick milk heating.

During such phase, if Venturi valve 33 is missing, being both valves 31and 32 open, an over-pressure, estimated for instance at 50 mbar aboveatmospheric ambient pressure, is present in Venturi 22 a and preventsair from flowing from the surrounding environment into Venturi 22 a.

During such phase, if the nonreturn valve is provided, steam flowtowards the surrounding environment is in any case prevented.

In a second phase, for instance upon thermometer 27 signalling tocontrol unit 25 a first predetermined temperature, e.g. a temperature of30°, control unit 25, according to the programs developed during thedesign phase of device 10, commands the closure of the first valve 31and the opening of Venturi valve 33.

Due to the closure of the first valve 31, a depression capable of makingair flow from the surrounding environment into steam, is generated inVenturi 22 a.

The Applicant has experimentally detected that, taking into account thepressure values assumed in boiler 12, pressure in the Venturi is in therange 260 to 130 mbar below atmospheric ambient pressure, and is such asto enable air flow from the surrounding environment into duct length 42.

Air mixed with steam arrives at nozzle 14 and hence to milk 19 containedin the container, where milk begins frothing and grows by embodyingsmall air bubbles at its interior. In such phase, steam in the air/steammixture leaving nozzle 14 continues heating milk, of course at lowerspeed than in the first phase, since steam arrives from second duct 22only. Yet, such slow heating condition is ideal for producing ahigh-quality froth or cream.

In a third phase, for instance upon thermometer 27 signalling to controlunit 25 a second predetermined temperature, e.g. a temperature of 55°,control unit 25, according to the programs developed during the designphase of device 10, commands the opening of the first valve 31 and theclosure of Venturi valve 33.

In such phase, similarly to the first phase, a strong steam flow to thenozzle and a correspondingly high speed of milk heating occur.

During such phase, if Venturi valve 33 is missing, the indicationsalready provided for the first phase still apply.

In a fourth phase, for instance upon thermometer 27 signalling tocontrol unit 25 the maximum milk heating temperature, control unit 25,according to the programs developed during the design phase of device10, commands the closure of the first and second valves 31 and 32,respectively, and signals the completion of frothed milk preparationthrough signalling unit 38.

The operation of device 10 for preparing a heated beverage, e.g. milk,is as follows.

Upon actuation in a first phase of key 39 b intended to startpreparation, for instance, of heated milk, control unit 25, according tothe programs developed during the design phase of device 10, keepsVenturi valve 33 closed and commands the opening of both the first valve31 and the second valve 32, which therefore enable the quick steam flowfrom nozzle 14 and a correspondingly quick milk heating, similarly towhat has been already described for the first phase of frothed milkpreparation.

During such phase, all indications already given for the first phase offrothed milk preparation apply.

In a second phase, for instance upon thermometer 27 signalling tocontrol unit 25 the maximum milk heating temperature, control unit 25,according to the programs developed during the design phase of device10, commands the closure of the first and second valves 31 and 32,respectively, and signals the completion of heated milk preparationthrough signalling unit 38.

According to the above description, in the preferred embodiment, atleast three operating temperatures, stored for instance in the controlunit, are envisaged for preparing frothed milk:

-   -   a first operating temperature t1, corresponding to the        temperature, e.g. 30°, at which air introduction into steam        starts;    -   a second operating temperature t2, corresponding to the        temperature, e.g. 55°, at which air introduction into steam        ends;    -   a third operating temperature t3, e.g. 70°, corresponding to the        maximum milk heating temperature.

According to one of the three possible embodiments, it is envisaged thatthe third temperature t3 is set and possibly stored into the controlunit through parameter setting unit (ancillary keyboard) 37, and thatthe first and second temperatures, t1 and t2, respectively, aredetermined by control unit 25 and stored based on froth level parameters(e.g. low, medium, high) set through ancillary keyboard 37.

As the skilled in the art can readily realise, as the froth level havingbeen set increases, the control unit is arranged to determine, accordingto the programs developed during the design phase of device 10,increasing temperature intervals t1-t2, so as to broaden the temperaturerange and, consequently, to increase the time during which air is mixedwith steam.

Of course, other embodiments provide for the possibility of directlysetting all temperatures t1, t2 and t3, respectively.

As the skilled in the art can readily realise, the provision of Venturivalve 33 enables, by keeping Venturi valve 33 always closed, a variablespeed heating of the beverage, for instance, by setting heating speedparameters (e.g. low, medium and high speed) through ancillary keyboard37.

Actually, by keeping Venturi valve always closed 33 and by controllingthe opening and the closure of the first and second valves 31 and 32,respectively, the beverage heating speed can be changed without thebeverage being frothed.

Such a feature is particularly useful when preparation of hot beverages,such as hot chocolate or mulled wine, is desired. In such cases, indeed,a too high heating speed could negatively affect the quality of theresult, whereas higher heating speeds can be used for other beverages.

The preferred embodiment provides for having a thermometer associatedwith nozzle 14 and connected to control unit 25.

Of course, in other embodiments, the thermometer can be missing and thecontrol for preparing e.g. frothed beverages can be performed by thecontrol unit based on parametrical times, corresponding for instance, tothe time necessary for reaching temperature t1, the time necessary forreaching temperature t2 and the time necessary for reaching temperaturet3. The same method can be applied also to preparing heated beverages.

Of course, obvious changes and modifications can be made to the abovedescription, in respect of sizes, shapes, materials, components, circuitelements and connections, as well as in respect of the details of thedisclosed construction and the operating method, without departing fromthe invention as defined in the following claims.

1. A device for heating and/or frothing a beverage, comprising: a firstduct connectable to an upstream steam source and to downstream mixingmeans (14) arranged to introduce and mix at least steam into saidbeverage, said first duct having a first valve configured to be openedand closed and to enable or prevent steam flow into the duct; a secondduct connectable to the upstream steam source and to said downstreammixing means, said second duct having a second valve configured to beopened and closed and to enable or prevent steam flow into the duct;wherein a first one of said two ducts comprises a Venturi assemblyconfigured to operate by Venturi effect in order to mix air with saidsteam in said first one of said two ducts when a second one of said twoducts is closed.
 2. The device as claimed in claim 1, comprising afurther valve connected to the Venturi assembly and configured to enableair flow into said Venturi assembly and to prevent steam flow out ofsaid one of said two conducts.
 3. The device as claimed in claim 1,wherein said Venturi assembly includes an orifice having a determinedinternal diameter, and is connected to a duct length having a respectiveinternal diameter smaller than the internal diameter of said orifice. 4.The device as claimed in claim 1, further comprising a control unitconnected to said first and second valves and configured to control theselective opening and closure of said first and second valves.
 5. Thedevice as claimed in claim 2, further comprising a control unitconnected to said first and second valves and configured to control theselective opening and closure of said first and second valves.
 6. Thedevice as claimed in claim 3, further comprising a control unitconnected to said first and second valves and configured to control theselective opening and closure of said first and second valves.
 7. Thedevice as claimed in claim 4, further comprising a third valve connectedto the Venturi assembly, and wherein said control unit is configured tocontrol the selective opening and closure of said third valve.
 8. Thedevice as claimed in claim 5, further comprising a third valve connectedto the Venturi assembly, and wherein said control unit is configured tocontrol the selective opening and closure of said third valve.
 9. Thedevice as claimed in claim 6, further comprising a third valve connectedto the Venturi assembly, and wherein said control unit is configured tocontrol the selective opening and closure of said third valve.
 10. Thedevice as claimed in claim 4, further comprising temperature detectingmeans, which are associated with said mixing means, are connected tosaid control unit and are arranged to transmit signals representing thetemperature of said beverage to said control unit.
 11. The device asclaimed in claim 7, further comprising temperature detecting means,which are associated with said mixing means, are connected to saidcontrol unit and are arranged to transmit signals representing thetemperature of said beverage to said control unit.
 12. The device asclaimed in claim 10, wherein said control unit is configured to controlheating and/or frothing of the beverage based on the temperaturedetected by said temperature detecting means.
 13. The device as claimedin claim 4, further comprising a command unit connected to said controlunit and comprising command means arranged to selectively commandpreparation of either a heated or a frothed beverage.
 14. The device asclaimed in claim 7, further comprising a command unit connected to saidcontrol unit and comprising command means arranged to selectivelycommand preparation of either a heated or a frothed beverage.
 15. Thedevice as claimed in claim 10, further comprising a command unitconnected to said control unit and comprising command means arranged toselectively command preparation of either a heated or a frothedbeverage.
 16. The device as claimed in claim 12, further comprising acommand unit connected to said control unit and comprising command meansarranged to selectively command preparation of either a heated or afrothed beverage.
 17. The device as claimed in claim 4, comprising aparameter setting unit connected to said control unit and comprisingparameter setting means configured to store into said control unitparameters to be used for preparing a heated or frothed beverage. 18.The device as claimed in claim 7, comprising a parameter setting unitconnected to said control unit and comprising parameter setting meansconfigured to store into said control unit parameters to be used forpreparing a heated or frothed beverage.
 19. The device as claimed inclaim 17, characterised in that said parameters include at least onetemperature range for frothed beverage preparation.
 20. A machine forpreparing hot beverages, in particular espresso coffee, characterised inthat it includes a device as claimed in claim 1.